The invention relates to an airbag module and more specifically to an airbag module which controls the rate and direction of expansion of an associated gas bag.
Passenger airbag modules are disposed in the dashboard in front of the passenger seat and have a housing in which a tubular generator is disposed. Above this tubular generator a gas bag extends in the direction of the passenger over the entire length of the tubular generator, as is known, for example, from U.S. Pat. No. 4,191,392 and from European Patent No. A-0 602 785. In a housing cover located between the tubular generator and the gas bag, openings are located on either side of the tubular generator over its entire length, through which openings the gases escaping from the generator enter the gas bag through its inflation port upon firing of the generator in the event of a crash. In a self-contained airbag arrangement, wherein the tubular generator is disposed inside the airbag with a supporting housing and is enclosed by it, the openings are on the sides of the tubular generator and extend over its entire length. As a result of the side position of the openings, the gas bag is thus inflated over its entire length first on its sides before it opens completely.
This prior art arrangement of the passenger airbag module has the disadvantage that the side sections of the gas bag, where it is attached, are particularly heavily stressed upon inflation. These stresses may result in the tearing off of the gas bag from its anchoring. Consequently, in prior art passenger airbag modules, the edge of the inflation opening is reinforced and stitched several times, resulting in additional production time and costs.
The danger also exists that the split cover which covers the gas bag relative to the passenger compartment does not tear, as desired, in the center, but on the side instead.
The aforementioned disadvantages also exist, although to a lesser extent, in a driver airbag module in which a prior art gas generator which has the shape of a shallow can is used.
It is further known from European Patent No. A-0 620 140 to place a diffuser between the gas generator and the gas bag. The diffuser has, on the entire length of the gas generator, numerous openings through which the gas may flow into the gas bag in the event of a crash. Further known, from EP 0 607 671, is a hybrid gas generator which has a centrally disposed diffuser with side flow openings.
Even these arrangements of the diffuser have the aforementioned disadvantages since the gas bag is bombarded with gas in all cases upon deployment virtually simultaneously over its entire surface above the diffuser and is explosively pushed out of the housing. Thus, the gas bag pack as a whole is greatly accelerated and pushed out of the module housing, whereby the surface stressing of the module cover is great and high bursting forces thus occur.
From U. S. Pat. No. 4,332,398, an inflatable restraint system is known which has a tubular gas generator, a cylindrical diffuser, and a flow control arrangement connected to these. This arrangement terminates in a nozzle which extends, in the inactivated state of the restraint system, into the partially deployed gas bag, whereby most of the gas bag is folded next to the gas generator. The cylindrical diffuser is positioned at the rear of the nozzle and has openings for the discharge of the gas. In additional to the control arrangement with the nozzle, retarders are present which press the gas bag against the walls of the control arrangement. These additional structural elements are claimed to prevent the conventional explosive inflation of the gas bag. As a result of the friction between the gas bag on the one hand and the control arrangement and the retarders on the other, the inflation is decelerated, particularly at the beginning of the inflation process.
This restraint system has the disadvantage that additional components are necessary to achieve a delayed opening of the gas bag.